DESCRIPTION (Applicant's Abstract): Over 14 percent of persons diagnosed with AIDS in South florida and 10 percent nationally are over age 50 years. Although HIV infection is frequently accompanied by cognitive impairment without disorder, minor cognitive-motor disorder (MCMD) or HIV-associated dementia (HAD), few HIV+ individuals over age 50 years have been studied to date. Yet, HIV-associated disease progression may be more rapid in older individuals, and HIV affects many of the same cognitive processes altered by aging. Further, age appears to be an independent risk factor of HAD. The overall objective of the proposed study is to determine whether aging and HIV infection have a synergistic effect on the frequency and rate of progression of cognitive impairment and cognitive-motor disorder (MCMD and HAD). That is, are the effects of both aging and HIV on cognition significantly greater than the simple sum of the effects of each one alone? If so, these effects on cognition are expected on self-perceived functional status related to cognition and on the level and rate of decline in overall activities of daily living. Age has been associated not only with decreased CD4 cell count in HIV+ individuals but also with increased plasma viral load. Hence, it is hypothesized that older HIV+ individuals will show increased viral load and decreased CD4 cell count (as well as rate of change) than the comparison groups, controlling for anti-retroviral medication use (and adherence), CDC stage of disease, hemoglobin level, and other factors related to clinical disease progression. Moreover, the investigators have recently reported that cognitive-motor impairment in the otherwise asymptomatic stage of infection is associated with an increased risk of mortality. A longitudinal study is proposed herein of 286 total subjects -- 106 late symptomatic (AIDS-diagnosed) individuals (53 older, 53 younger); 106 early symptomatic (non-AIDS) HIV+ individuals (53 older, 53 younger) and 74 HIV- control subjects (37 older, 37 younger). Performance on a cognitive battery sensitive to HIV serostatus; cognitive-motor impairment and disorder (MCMD and HAD); functional status; plasma HIV load; CD4 cell count; and mortality are the proposed outcomes, controlling for sociodemographics, distressed mood, Axis I disorder, physical health status, alcohol/psychoactive substance use, prescribed medication use, pain, fatigue, and nutritional status.